[Part 1 begins with a look at the two basic radiation patterns of sound sources. Part 2 answers the question "If we want to measure a loudspeaker, and from those measurements try to anticipate how it might sound in a room, what should we measure?" Part 3 reviews results of the author's elaborate subjective-objective investigation into loudspeaker evaluation.]

18.4 THE REAL WORLD OF CONSUMER LOUDSPEAKERS
It is important to have a perspective on where we stand at the present time; what kinds of products are in the marketplace? Measurements of the kind being shown here are almost never on public display, so the following is a brief tour of some real-world products, good and not-so-good.

To be fair, no brands are mentioned because things can and do change. Past performances are not always reliable indicators of future performances, and it can go either way: up or down. The purpose is merely to provide the readers with enough visual data to allow them to see that there are recognizable patterns in the measured performances of loudspeakers that are awarded high ratings in double-blind listening tests.

One can only hope that one day data of this kind will be readily available to consumers, to help them in choosing products, and to reviewers, to help them explain some of the things that they hear. Arguments that families of curves like this are too complicated for common consumers to understand have merit, but does this justify displaying specifications data so simplified that all meaning is lost?

Understanding and interpreting specifications is the duty of salespeople, and, as can be seen, no advanced degrees are required. If this kind of comprehensive data were suddenly available, the industry would undoubtedly suffer some angst as manufacturers adjust to the new, more level playing field. There may even be rebellion in some quarters, but such are the consequences of change.

The automobile industry is a good example of one that has come to face the reality that their products will be subject to highly technical analysis as well as to demanding subjective evaluations. Sometimes the numbers and the opinions correlate better than others, but there is always a correlation. Being interested in cars, I have observed that some enthusiast magazines are seriously exploring new telemetric measures that do better at describing what is happening - lateral G force, slip angle, steering angle, and so on - at 100 mph in a decreasing-radius left-hand turn. Compared to this, showing a collection of frequency response curves on a simple product, decent examples of which are in the price range of tires and wheels, seems utterly trivial.

What is not trivial is the matter of production quality control. It is one thing to build a superb prototype, but it is a very different matter to duplicate that performance in mass production. A few manufacturers have impressive measurement capabilities on production lines - better perhaps than others have in their engineering labs. Sadly, this is the one reason why even honest specifications can mislead, because consumers have no option but to trust that all products with the same brand and model are the same. In some cases, they are amazingly similar, but in others . . . .

Were any Tannoy-type dual-concentric designs examined? The amplitude charts supplied with my 8in DC2000s are smooth and within a few dB across the range, apart from a designed-in 'fashion' bump around 50Hz. These drivers must surely have been improved upon by now?
I would be interested to know your directionality test method, to check that aspect; they have always been spectacularly sharp in their imagery, but I have never been able to decide if their sensitivity to positioning is due to their ability to accurately 'probe' the environment or if the units had some funny characteristics of their own. I think they have about +/-45deg dispersion with essentially no phase or frequency problems, deteriorating beyond that.